Kidney diseases generally include pathological conditions in the acute and chronic phases, and particularly chronic kidney disease affects about 11% of adults in Japan, the number of which is increasing year by year (Non-patent Literature 1). With decrease in kidney function, chronic kidney disease worsens into uremia due to accumulation in the body such as blood of a harmful toxic substance (a uremic toxin) which is in principle to be excreted from the body. It is thought that uremia itself induces further kidney dysfunction and also does promote progression of chronic kidney disease, although uremia may cause muscle weakness, abnormal sensation, and even hypertension, anemia and cardiac hypertrophy in addition to sleeplessness, headache, bad breath, and appetite reduction (Non-patent Literature 2).
Orally administered adsorbents have attracted attention as an agent that can remove uremic toxins from the body and treat renal and hepatic dysfunctions. Specifically, an adsorbent as disclosed in Patent Literature 1 comprises a porous spherical carbonaceous substance having specific functional groups (hereinafter sometimes referred to as “spherical activated carbon”) and can achieve intestinal adsorption and excretion in feces of uremic toxins and precursors thereof (for example, indoleacetic acid) accumulated in vivo, resulting in a reduction in the uremic toxins (for example, indoxylsulfuric acid) in the blood. As agents that can attain such an object, some adsorbents for oral administration comprising spherical activated carbon have been developed so far, and the use of those adsorbents reportedly can suppress kidney injury and delay the induction of dialysis. (Patent Literature 2, Patent Literature 3, Non-patent Literature 3, Non-patent Literature 4, Non-patent Literature 5, Non-patent Literature 6 and Non-patent Literature 7).
Adsorbents for oral administration comprising spherical activated carbon, however, have some disadvantages; these adsorbents have insufficient adsorption performance and are to be administered at high daily doses accordingly, which causes gastrointestinal symptoms, such as constipation and anorexia. In particular, patients with chronic kidney disease, who must control water intake, have to swallow a high dose of 6 g per day of adsorbents for oral administration comprising spherical activated carbon with a small amount of water, which imposes a great strain on the patients.
Presently, hemodialysis enables chronic kidney disease patients with lost kidney function to survive for a longer period, and the advent of dialysis therapy has brought great gospel to many of the patients. However, unless renal transplantation is carried out, the dialysis therapy, which entails chronic complications such as itching and anemia, has to be continued for life and imposes a great mental and physical strain on the patients. It is often reported that accumulation of uremic substances in the body is involved in development of dialysis complications (Non-patent Literature 8), and it is, therefore, a problem how to greatly and rapidly reduce harmful substances that are unable to be removed at all or sufficiently by dialysis from the body.
In addition, other orally administered adsorbents include medicinal carbon (sometimes referred to hereinafter as “powdered activated carbon”). Orally administered medicinal carbon can be used as one of therapeutic approaches to acute drug intoxication that occurs when agrichemicals such as insecticides and herbicides, analgesics and hypnotics are intentionally or accidentally administered in high doses for a short time, which is a pathological condition causing consciousness disorder, respiratory and/or circulatory disorders, or disorders of organs such as kidney and liver. The medicinal carbon can adsorb or precipitate a poison present in the digestive tract to suppress absorption of the poison into the body. The medicinal carbon is required to be administered in an amount of 40 to 60 g per kg of body weight for adults and of 1 g even for children (Non-patent Literature 9), which indicates that adsorption performance of the medicinal carbon as a uremic toxin adsorbent is unclear.